Field of the Disclosure
This invention relates to the synthesis of diiodoperfluoro-C3 to C7-alkanes (I(CF2)nI, wherein n is 3 to 7, under moderate pressure conditions.
Description of the Related Art
Examples 1 through 11 of U.S. Pat. No. 6,002,055 disclose the reaction of hexafluoropropylene oxide (HFPO) with iodine under autogenous pressure in a reactor at 185° C., with and without the presence of a catalyst, to obtain diiodomethanes and their homologues. The HFPO/iodine reaction is disclosed in the reaction equation (II) (col. 3, I. 25) to form one mol of CF3COF (perfluoroacetyl fluoride)(PAF) by-product for each mol of HFPO consumed in the reaction. Example 1 discloses the formation of 184 g of PAF from 266 g of HFPO reactant. The problem presented by the formation of the PAF in the reactor as a result of the HFPO/iodine reaction is that the PAF, especially towards the end of the reaction when the PAF formation is approaching its peak, causes the autogenous pressure within the reactor to become very high, requiring the use and expense of a high pressure resistant reactor and auxiliary equipment including seals.
WO 2014/062450 discloses the HFPO/iodine reaction being carried out in the presence of certain combinations of Ni and Mo as a catalyst that minimize the production of I(CF2)nI, wherein n is 1 or 2 during the synthesis of I(CF2)nI, wherein n is 3 to 11. In the Examples of the invention, the reaction is carried out at temperatures of 170° C. to 185° C. (Examples 1-3 and the batch temperatures in Table 4). No mention is made of the formation of PAF in the reaction even though its formation is inevitable. COMPARATIVE EXAMPLE A, however, discloses the cooling of the reaction autoclave to room temperature, followed by the venting of gases. This venting would include the total amount of PAF formed in the reaction.